SQL: Syntax error with intersect?

问题

This is my query:

-- Sids of suppliers who supply a green part AND a red part
(SELECT Suppliers.sid
FROM Suppliers
JOIN Catalog ON Catalog.sid = Suppliers.sid
JOIN Parts ON Parts.pid = Catalog.pid
WHERE Parts.color = "red")
INTERSECT
(SELECT Suppliers.sid
FROM Suppliers
JOIN Catalog ON Catalog.sid = Suppliers.sid
JOIN Parts ON Parts.pid = Catalog.pid
WHERE Parts.color = "green");

This is the error:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near "INTERSECT (SELECT Suppliers.sid FROM Suppliers JOIN Catalog ON Catalog.sid = Sup" on line 6.

What am I doing wrong?

This is the schema:

Suppliers(sid: integer, sname: string, address string)

Parts(pid: integer, pname: string, color: string)

Catalog(sid: integer, pid: integer, cost: real)

bold = primary key

回答1:

MySQL, which you appear to be using, does not support the INTERSECT syntax. You're going to have to solve it another way.

In this case, it is trivial -we only need a list of all suppliers that offer "green" and "red" of some part- your query does not bother to see if the parts themselves are related, so we can solve it quite easily like this:

SELECT Suppliers.sid
FROM Suppliers
JOIN Catalog ON Catalog.sid = Suppliers.sid
JOIN Parts ON Parts.pid = Catalog.pid
WHERE Parts.color IN ('red', 'green')
GROUP BY Suppliers.sid
HAVING COUNT(DISTINCT Parts.color) = 2

Personally, I don't believe the original query is a typical INTERSECT problem. Take a look at the JOIN solution offered by Vinko Vrsalovic for a general solution to emulate the INTERSECT (which I would btw prefer even if the RDBMS would in fact offer INTERSECT natively).

回答2:

Nothing, MySQL doesn't have the INTERSECT keyword. You can rewrite it as an INNER JOIN:

SELECT DISTINCT sid FROM
(SELECT Suppliers.sid
FROM Suppliers
JOIN Catalog ON Catalog.sid = Suppliers.sid
JOIN Parts ON Parts.pid = Catalog.pid
WHERE Parts.color = "red") a
INNER JOIN
(SELECT Suppliers.sid
FROM Suppliers
JOIN Catalog ON Catalog.sid = Suppliers.sid
JOIN Parts ON Parts.pid = Catalog.pid
WHERE Parts.color = "green") b
ON (a.sid = b.sid);

This query can surely be better written, but this is to show that intersect is but merely an inner join with a select distinct, you can automatically transform one into the other.

回答3:

This should do what you want:

SELECT Suppliers.sid
FROM Suppliers
JOIN Catalog ON Catalog.sid = Suppliers.sid
INNER JOIN Parts AS parts1 ON parts1.pid = Catalog.pid AND parts1.color = "red"
INNER JOIN Parts AS parts2 ON parts2.pid = Catalog.pid AND parts2.color = "green"

回答4:

Another solution in order to use INTERSECT in MySQL is to use IN clause. Problem: "Find course id’s of courses offered in Fall 2009 and Spring 2010"

//DML sample
(select course_id
from section
where semester = ‘Fall’ and year = ‘2009’)
intersect
(select course_id
from section
where semester = ‘Spring’ and year = ‘2010’);

In MySQL:

select distinct course_id
from section
where semester = 'Fall' and year= 2009 and
course_id in (select course_id
from section
where semester = 'Spring' and year= 2010);

If you need more on IN clause , please search on Google.

来源：https://stackoverflow.com/questions/2302873/sql-syntax-error-with-intersect

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sql

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intersect